This relates generally to imaging systems and, more particularly, to imaging systems with in-pixel anti-blooming diodes.
Modern electronic devices such a cellular telephones, cameras, and computers often use digital image sensors. Imagers (i.e., image sensors) often include a two-dimensional array of image sensing pixels. Each pixel typically includes a photosensor such as a photodiode that receives incident photons (light) and converts the photons into electrical signals.
In conventional image sensors, over of a photosensor to light can cause charge from a saturated pixel to “bloom” into neighboring non-saturated pixels, which in turn can cause the neighboring pixels to exhibit a non-linear response to light. To avoid undesirable image artifacts that can result from blooming charge, conventional image sensors sometimes hold a floating diffusion region at a reference potential during integration so that excess charge flows into the floating diffusion region and away from adjacent photodiodes. However, this type of configuration often leads to increased dark current generated under the transfer gate due to the voltage that is necessary to allow charge to flow from the photodiode to the floating diffusion region.
It would therefore be desirable to be able to provide image sensors with improved anti-blooming circuitry and minimized dark current.